First thing, is that the lights are brilliant, why on earth anyone would want to convert to 12V is beyond me. If anything, the charging system is too good, with the ammeter showing a charge at all times UNLESS you have the lights on the "battery" setting. Put them "off" or on "direct" and you have about a 2 amp charge..

Anyway, sticking with 6 volts. I am using the original rectifier.. I know that everyone throws these away and fits a "modern" bridge rectifier, but, and this has bothered me for some time, how on earth do you wire it up???

The bike was built so that you have one lighting coil charging all the time, whether the lights are "off" or set to "pilot", and then, when you turn the head lamp on, the two other coils get connected too, so you have three coils charging.

How can you do this with a bridge rectifier?? So far as i am concerned, it is completely impossible, as, the two coils, are not in phase with the third, so you have a choice, either use the one, or two, but not three,

Fit a bridge rectifier and you are going backwards in a BIG BIG way by partially shorting out your lighting coils.. [and worse!!!] i will talk about the "even worse" bit later..

Debate......

john..

Last edited by john87 on Mon Nov 13, 2017 9:34 am; edited 1 time in total

The main problem with ancient selenium rectifiers is that they tend to allow a reverse current flow which will flatten the battery. If you use the Forum 'Search' function you will find lots of discussions on this subject. I had to replace the original rectifier on my AMC/Wipac Falcon 87 for this reason, but the Villiers/Westinghouse rectifier on my Falcon 81 still soldiers on.

It is possible to get poly phase full wave rectifiers that would allow all 3 coils to charge the battery. An example RS number 0462067 on the RS website. There is a pin on the rectifier package for the output of each of your coils.

Farley wrote:It is possible to get poly phase full wave rectifiers that would allow all 3 coils to charge the battery. An example RS number 0462067 on the RS website. There is a pin on the rectifier package for the output of each of your coils.

Don't quote me, but would a 3 phase Podtonics type power box not work?

Things have advanced since uncle Joe Lucas started to use the zener diode to regulate the voltage. Now we have a combined rectifier and regulator in one product. Feed it AC and it provides smooth DC at the correct level to charge batteries. They make them in single and 3 phase versions. No more boiled batteries.

On my Plover 86 (different set up I know)the charging coils have more turns than lighting coils and it is only the charging coils that are connected to the rectifier. The lighting coils give out to low a Voltage to charge the battery.

It gets better. Look at the wiring diagram for the bridge rectifier above, and then look at the "schematic" i posted..

Draw out the current path, and you will see that when the output from a coil is on the positive half cycle, it flows through the rectifier, through the battery, back, via the bike frame, to the coil. Yeh, a complete circuit like we want.

Now draw out the current path for the negative half cycle.. You will see that the rectifier shorts the coil directly to earth!!!

Great for the coil!! And then folks all wonder why their rectifier gets hot!!!! ha ha ha

Having checked what a Falcon 81 is, ie a Villiers flywheel generator.It is a normal 9E Villiers setup. The two pin plug on the engine casing, sends the bulk of the AC to the lights, with the smaller black wire sending its AC to the rectifier. †It is only half-wave rectified, enough to charge the battery, it also taps into the headlamp switch, adding any extra current to the lights. †See diagram.

No, see the simplified diagram i have posted.. The single coil goes through the rectifier to the ammeter and then the battery. The two coils are not in circuit until you switch the headlights on. Then, TWO things happen;1, Current flows to terminal "1" in the switch which is linked to "2" and then by the roller with "D" written on it to terminal "3" and the headlight. AT THE SAME TIME see the two "toggles" in the top of the switch?? They both decend, [see the chart] and connect the two coils to the rectifier, and hence the ammeter, and the battery.

As can be seen, this is a clever well thought out solution and changing it is a big step backwards. Forget all about bridge rectifiers, if your original rectifier is knackered [doubt it it is hermetically sealed] all you need to do is to insert TWO diodes. One in the dark green wire, one in the light green, and then connect BOTH diodes to the purple wire.. You could if you wanted, take the original rectifier to bits and fit the diodes inside it .

FOLLOW THE CURRENT PATHS and you will see what i mean.

If you must use a bridge rectifier, that is up to you, but NO TERMINAL FROM THE RECTIFIER GOES TO EARTH [Unless that is, you want to short your coils out every negative half cycle...]

I have replaced the old Wipac twin diode selenium rectifier from my Cruiser 89 with a modern rectifier/regulator from Electrex. This is possible on the 2T because the alternator charging coils are not connected to earth. (The original wiring uses a centre tapped coil and the two diodes to give full wave rectification)

One common problem reported with the old selenium rectifier diodes is the progressive increase in forward volt drop (spec states approx. 1.0 V for new device) . I decided to check this on the old 1963 vintage rectifier (Wipac type S2642) from my 89. Test results:At 2 A. load the volt drop across the individual diodes was 1.2 V. increasing to 1.5 V. at 4.0A, which equates to the rectifier dissipating 6 Watts with main beam selected. Reverse current was 2mA @ 6 V.For comparison a 5 A, 30 V shottky rectifier diode had a forward volt drop of 0.46 V @ 4.0 A. giving power loss of 1.8 W. Reverse current less than 0.01 mA @ 6 V.It can bee seen that the modern silicon diode is far more efficient than an old selenium device. i.e. giving approx 4 W more for the head light.

One easy, if expensive, way to improve the lighting and lighten the load on the old electrical system is to use LED lamps. The latest LED BPF head lamps give a brighter light output for about one third of the current taken by a filament lamp. My bike ammeter, with full beam lighting selected, shows about 1.5 A discharge!

The basic, fairly cheap bridge rectifier, come with convenient tags. They can also be placed somewhere to keep cool. They can be mounted, using the hole in the middle, making a heat sink withthe mounting point. They wll take about 10A plus (yes I know this is way beyond Villiers reaching the limit). They are far more readily available than single diodes. Costs about £2.50 on eBay .

1N4007 diodes, which on eBay are £1.00 for 10, but only have an average current rating of 1A or 6W on a Villiers system whilst being far cheaper, will need to be connected to the wiring harness.